1. Field of the Invention
The present invention relates to an In-Line sampling device and method for withdrawing (aspirating) blood from a patient fitted with a blood vessel catheter. More particularly, the present invention relates to a syringe enabled for aspirating blood into a sampling site in a closed manner, sealed from ambient air, in order to reduce the risk of human error and cross contaminations during the sampling process. Still more particularly, the present invention relates to a syringe, designed to operate manually or automatically and in synchronization with a sampling stopcock valve.
2. Prior Art
Sealed sterile blood sampling systems are known that have a dual function of introducing an upstream sterile fluid (e.g. saline solution) to a patient located downstream, and drawing back (aspirating) upstream fluid into the syringe. In a typical system, a small amount of infused fluid runs through the blood sampling line to the patient, when the line is not in use. This enables the blood sampling line to be maintained in a clear, unblocked/unclogged condition. When it is desired to take a blood sample from the patient, the fluid is aspirated beyond the sampling site so that a clean blood sample may be withdrawn. Relevant prior art documents that describe aspirating syringes or other syringe like aspirating devices said fluid sampling devices include the following.
U.S. Pat. No. 5,324,266 & U.S. Pat. No. 5,265,621 describe inline syringes which are operated linearly, namely the aspiration is performed by manually pulling the internal part of a syringe. This procedure may be physically strenuous due to the resistance of the gasket inside the syringe which may lead to accidental over aspiration. These patents further describe a sealing sleeve for maintaining a closed environment inside the syringe. This sleeve moves during aspiration, which can lead to ruptures or disengagement of the sleeve resulting in breach of the closed system. The linear operation of the syringe results in the extension of a piston beyond the syringe by a displacement equivalent to the aspirated volume, essentially doubling the length of the syringe. This is cumbersome in a hospital setting, and especially strenuous on a patient's arm. Additionally, operation of this “linear style” syringe requires the use of two hands, one to extract the piston, the other to prevent the syringe from moving.
U.S. Pat. No. 5,961,472 discloses a syringe which can be operated single handedly as opposed to the previous two patents discussed. However this syringe requires two independent squeezing motions instead of one, is not inline, and thus requires an additional valve system.
U.S. Pat. No. 5,374,401 discloses a blood sampling apparatus that uses a rotational movement to linear displacement of a piston via a threaded transmission system. This type of transmission involves high resistance due to friction of the thread. As a result high torque is exerted on a patient's arm (or stand) and could mask resistance of the fluid line due to occlusions. In addition this apparatus does not operate in-line and therefore requires an additional valve system, and is cumbersome to clean after aspiration. The exact amount of fluid aspirated is hard to determine as this apparatus does not incorporate a scale or any other measurement means.
U.S. Pat. No. 6,159,164 discloses a blood sampling system that does not operate in-line and therefore requires an additional valve system, and is cumbersome to flush and clean after aspiration. The exact amount of fluid aspirated is hard to determine as this apparatus does not incorporate a scale or any other measurement means. This system is operated by manually pushing an actuator towards the vertical axis of the apparatus which may result in torque that dislocates the apparatus from a patient's arm.
There are automatic systems for blood aspiration, for example, such as described in the U.S. Pat. No. 7,680,042 and US Published Patent Application No. US201010217154 and some of these systems incorporate use of integrated pressure monitoring. However, these systems cannot be operated manually, and most important, these systems do not operate in a closed manner, which allows the return of dead space fluids to patient, rather they discard these fluids as they are contaminated once aspired. In addition to the loss of fluids, working with systems that are not closed may result in higher contamination risks.
U.S. Pat. No. 5,758,643 is an example of a system that works in a closed manner and can return the dead space fluids to a patient; however, this system cannot operate manually and does not have an integrated pressure sensor for monitoring blood pressure.
None of the prior art described herein above enables the use of an automatic mode for aspirating syringes using an electronic system. Furthermore, pressure monitoring is required in many applications which require blood sampling; none of the prior art described above enable a device integrated pressure monitoring application.